Liberia's president has declared a curfew and ordered security forces to quarantine a slum home to at least 50,000 people as the West African country battled to stop the spread of Ebola in the capital.

The measures came as authorities said yesterday that three health workers in the country who received an experimental drug for the disease are showing signs of recovery, though medical experts caution it is not certain if the drug is effective.

At least 1,229 people have died of Ebola in Guinea, Liberia, Sierra Leone and Nigeria in the current outbreak, and more than 2,240 have been sickened, according to the World Health Organisation.

The fastest rising number of cases has been reported in Liberia, with at least 466 dead.

Authorities here have struggled to treat and isolate the sick, in part because of widespread fear that treatment centres are places where people go to die. Many sick people have hidden in their homes, relatives have sometimes taken their loved ones away from health centres, and mobs have occasionally attacked health workers.

Liberian President Ellen Johnson Sirleaf announced late yesterday that a curfew is going into place from 9 pm to 6 am (local time). Security forces also will be ensuring no one goes in or out of West Point, a slum in the capital where angry residents attacked an Ebola observation centre over the weekend.

"We have been unable to control the spread due to continued denials, cultural burying practices, disregard for the advice of health workers and disrespect for the warnings by the government," she said. "As a result and due to the large population concentration the disease has spread widely in Monrovia and environs."

"May God bless us all and save the state," she later added.

Saturday's attack on the observation centre in West Point was triggered by fears that people with the disease were being brought there from all over the country, the Information Ministry said yesterday.

Dozens of people waiting to be screened for Ebola fled the centre during the chaos. Looters made off with items, including bloody sheets and mattresses that could further spread the virus.